Pressure ratings on air compressors use different units and conventions that confuse buyers. Understanding bar, psi, gauge pressure and working pressure ensures the machine matches the tools and process.
The units
- Bar — metric unit, 1 bar is about atmospheric pressure at sea level
- PSI — pounds per square inch, common in North America
- Gauge pressure — pressure above atmospheric, usually marked barg or psig
Most industrial compressors are quoted in bar, with 7–8 bar the standard working pressure for general plant air and higher pressures for specialist processes.
Choosing the pressure rating
Match the compressor maximum pressure to the highest pressure required by any tool or process, plus the network pressure drop. Running a machine far below its maximum wastes efficiency, while running at the limit leaves no margin.
Common pressure levels
General workshop air is 7–8 bar, laser cutting 7–20 bar, PET blowing 30–40 bar, and high-pressure testing 100 bar and above. Choose the machine for the application, not for the highest number on the datasheet.